Document Type : Research Paper
Department of Architectural Engineering, Faculty of Engineering, Ilam University
University of Isfahan
University of Esfahan
The present article aims to analyze the status of the urban spatial system of Ilam province in the census period 1355 to 1395 using theories and models of urban system analysis such as; Rule of size-order order, modified order size model, entropy coefficient, Lorenz curve and Gini coefficient, two-city index, Mehta index, first-city focus index, Herfindahl concentration index, Henderson decentralization index Small (less than fifty thousand people) in the urban system of the province, in proportion to their population, and finally, by providing a balanced model of the appropriate urban system, will help to achieve sustainable urban development in the province.
The main question of this research is what model does the current situation of the urban system of the province follow? And what is the position of small cities in the urban system of the province?
This research is applied in terms of purpose and descriptive-analytical in terms of method. In this article, in order to collect the required data and information, the library method has been used to analyze the status of the urban system and the position of small cities in the province. Various indices such as, law of size - low order, modified order size model, entropy coefficient, Lorenz curve and Gini coefficient, two city index, two city index, Mehta index, first city focus index, Herfindhal concentration index, Henderson decentralization index It is used to show the distribution or concentration of the urban system and small cities in the period 1355 to 1395.
Calculations about the status of the urban system based on entropy coefficient show that in the periods 1355 to 1395 the province has a significant distance from the desired situation so that the values of entropy coefficient in the period 1355 to 1395 is indicative. The calculated values for the years 55, 65, 75, 85, 90, 95 are equal to 0.55, 0.58, 0.69, 0.67, 0.66 and 0.63, respectively, which indicate inappropriate spatial distribution and The number and population of cities in Ilam province are relatively unbalanced in urban classes. The highest distribution and imbalance are related to the period 1355 and the lowest distribution is related to the period 1375.
Studies and researches performed to analyze the spatial distribution of urban population in Ilam province using Lorenz curve and Gini coefficient in the census periods 55 to 95 show the imbalance of urban system pattern and instability in the urban system of the province.
Calculations based on Lorenz curve and Gini coefficient of 1355, 1365, 1375, 1385, 1390 and 1395 periods are equal to 0.65, 0.63, 0.67, 0.63, 0.66 and 0.71, respectively. In all periods, being close to one indicates an imbalance in the urban system. In these periods, the highest spatial distribution is related to the period of 2016 and the lowest is related to the periods of 1986 and 2006. The results are based on calculations performed by Lorenz curve and Gini coefficient, increasing the number of small cities despite reducing their population share in the model Urban system, demographic dominance of Ilam city as the first city, long distance from Lorenz curve and having an unbalanced Gini coefficient are the most important characteristics of the urban system of Ilam province.
The values of the first urban index in the periods 1355, 1365, 1375, 1385, 1390 and 1395 are equal to 0.50, 0.57, 0.49, 0.48, 0.48, and 0.49, respectively, which indicates the existence of the first pattern. Urbanization and the declining demographic role of small towns in the urban system. In all periods, almost half of the population of the province lives in the city of Ilam.
The values obtained for the two-city index for the periods 1355, 1365, 1375, 1385, 1390 and 1395 are equal to 4.65, 4.06, 5.37, 5.66, 55.5 and 5.89, respectively, which in all Periods have values with two significant intervals and these values also indicate an unbalanced pattern in the urban system of the province and the existence of the first urban pattern. The highest imbalance is related to the period 2016 and the lowest is related to the period 1986.
Calculations based on Mehta index in the periods 1355, 1365, 1375, 1385, 1390 and 1395 show the values of 0.64, 0.66, 0.64, 0.67, 0.67 and 0.68, respectively. This index indicates that if the ratio of the population of the first city to the total of the first four cities of the urban system is equal to 1.41, the urban system is balanced. And the small role of small towns.
According to the Herfindal concentration index, the higher the numerical value of this index, the more concentration we see in the urban system. Based on this index, the values of 0.29, 0.36, 0.27, 0.26, 0.26 and 0.27 have been calculated for the periods 1355, 1365, 1375, 1385, 1390 and 1395, respectively. The highest imbalance was related to the 1986 period and the 2006 and 2011 periods were more balanced.
The results of Henderson index in the periods 1355, 1365, 1375, 1385, 1390 and 1395 show the values of 3.41, 2.78, 3.72, 3.81, 3.85 and 3.76 that the Henderson decentralization index from 1355 to 2016 has an upward trend which shows a kind of spread and decentralization in the urban system of Ilam province, but in 2016 it has a downward trend.
Imbalance in the urban system and improper distribution of the number of cities in the population classes, reduction of the population share of small cities in proportion to their ranks, the existence of an unbalanced model of the urban system, the rule of the first urban model, long distances Small cities with the desired population size estimated based on the studied models and the large distance between the first city and the second cities and subsequent cities in the urban system of the province show the most important feature of the urban system of Ilam province. The existence of such an urban system, which shows the low status of the population to the detriment of small towns, has led to the emptying of small towns day by day.